Composition and oxidative stability of silflower (Silphium
integrifolium) seed oil and its potential as a new source of squalene
Abstract
Silphium integrifolium Michx. (silflower), a perennial plant, is of
great interest as a potential new oilseed crop due to its long, strong,
deep, extensive root systems, which can prevent erosion, capture
dissolved nitrogen, and out-compete weeds eliminating the need for
frequent irrigation and herbicide uses. In this study, oil was extracted
from unhulled silflower seeds, and its composition and oxidative
stability were evaluated. The oil content in unhulled silflower seeds
was 15.2 % (w/w), and its fatty acid composition was similar to that of
sunflower oil. The level of total polar compounds (TPC) in the oil was
12.3 % (w/w), and the content of total phenolics was 1.12 mg gallic
acid equivalent (GAE)/g oil. Noteworthily, 4.89 % squalene was isolated
from silflower oil indicating its potential application as an
alternative source of squalene. Silflower oil had lower oxidative
stability as indicated by the oxidative stability index (OSI) at 110 °C
and thermogravimetric analysis (TGA), presumably due to its high level
of chlorophyll (1002.8 mg/Kg). Even after a typical refining process
involving degumming, alkali refining, and bleaching with Fuller’s earth,
silflower oil contained 725.5 mg/kg chlorophyll, and its oxidative
stability was not improved. Further treatments with bleaching agents
including bentonite, sepiolite, and Tonsil® lowered the chlorophyll
level to 4.2, 474.5, and 38.5 mg/kg, respectively, and some aspects of
oxidative stability were improved and better than those of refined
sunflower oil. This study presents the potential of silflower oil as new
edible oil and a great plant source of squalene.